1. Field of the Invention
The present invention relates to a fuel rail (a delivery pipe) for supplying high-pressure fuel, which is supplied from fuel booster pumps of such as electronic fuel injection-type automobile engines, through a fuel injector (an injection nozzle) directly injecting into an engine cylinder. More specifically, the present invention relates to a fuel rail for high-pressure direct-injection internal combustion engines using a compression-ignition method or a spark-ignition method in a type for directly supplying fuel from a rail to an injector, and the manufacturing method of the fuel rail.
2. Description of the Related Art
As a fuel rail for direct-injection internal-combustion engines, there is a fuel rail for the gasoline engines in which main fuel is gasoline, and a fuel rail for the diesel engines in which main fuel is light oil. For example, for a fuel rail for direct-injection gasoline engines, fuel rails as described in the Japanese patent No. 3166090, Japanese patent No. 3885910, Japanese patent No. 4032383 and Japanese Patent Laid-Open No. 2007-16668 are known. In Japanese patent No. 3166090, a fuel rail comprising a communicating pipe and several cylindrical sockets, wherein the cylindrical sockets are formed by mold forming so that punched grooves bored in the communicating pipe can be covered, and a fuel-feeding hole is formed by boring each of the punched grooves to communicate with the inside of the cylindrical sockets, is disclosed. In Japanese patent No. 3885910, a fuel rail comprising components such as a main rail, a fuel-feeding pipe and a socket, the components are assembled by brazing, and then plating is performed on the whole product and an inner peripheral face of the pipe, is disclosed. In Japanese patent No. 4032383, a fuel rail comprising a main pipe and several branch pipes, wherein through-holes for receiving each branch pipe are formed to an outer wall of the main pipe, each through-hole has an annular wall which projects towards the outside and inside of the main pipe respectively, and each branch pipe is fixed to the annular wall, is disclosed. In Japanese patent Laid-Open No. 2007-16668, a fuel rail comprising a main rail having an injector holder, wherein the main rail and the holder are reciprocally connected while the injector holder is inserted into through holes provided in a peripheral wall section of the main rail, is disclosed.
Alternatively, in the case of a fuel rail for high-pressure direct-injection gasoline engines, for example, as for the connection of a fuel injectors (an injection nozzle), due to its O-ring seal structure, there might be a fuel leakage in the case of high pressure if a positional accuracy and roughness of a sealing surface are bad. On this account, especially in a fuel rail for high-pressure direct-injection internal combustion engines, machining process was required to assure positional accuracy and assembly accuracy. In the past, for this kind of fuel rail for high-pressure direct-injection gasoline engines, for example, such as a fuel rail for direct-injection internal combustion engines in which a machining process is performed on aluminum casting or an extrusion die (cf. Japanese patent Laid-Open No. 58-65970), or a fuel rail for direct-injection internal combustion engines which is constructed by assembling stainless-steel components by brazing or welding (cf. Japanese patent Laid-Open No. 2003-129920), are known. Moreover, for example, for a fuel rail for direct-injection diesel engines, fuel rails as described in the Japanese patent Laid-Open No. 2005-69023, Japanese patent Laid-Open No. 10-110883 and Japanese patent Laid-Open No. 2003-343387 are known. In Japanese patent Laid-Open No. 2005-69023, a fuel rail in which through holes are provided in a peripheral wall section of a cylindrical container or a peripheral wall section of a spherical container, and the fuel rail being constructed by reciprocally-connected while diverging branch pipes or branch connection metal fittings are inserted into the through holes, is disclosed. In Japanese patent Laid-Open No. 10-110883, a fuel rail having a flow passage inside a shaft core, a main rail made by brazing short-length block elements having a boss section which is provided with through holes communicating with the flow passage, in which the diverging branch pipes or branch connection metal fittings are connected to the boss section, is disclosed. In Japanese patent Laid-Open No. 2003-343387, a fuel rail comprising a main rail having branch connection metal fittings, wherein the main rail and the metal fittings are reciprocally brazed while the metal fittings are inserted into through holes provided in a peripheral wall section of the main rail, is disclosed.